Known disk drives for data storage systems comprise at least two disks mounted upon a spindle which is driven by a motor and an actuator assembly having a plurality of arm assemblies. Each arm assembly comprises at least an arm member one end of which is integral with the actuator body forming a portion of what is commonly referred to as an E block and a single or double head flexure assembly. A single head flexure assembly comprising a load beam connected to the arm member with a mounting plate, a gimbal connected to the load beam and a read/write head assembly connected to the gimbal. A double head flexure assembly comprises two load beams, one connected to the top of the arm member with a mounting plate and the other connected to the bottom of the arm member with a mounting plate, two gimbals, each respectively connected to one of the load beams, and two head assemblies each respectively connected to one of the gimbals. In the double head flexure assembly the two head assemblies are positioned back to back with one of the head assemblies facing upward and the other head assembly facing downward. A single arm assembly is associated with the top surface of the first disk and has its read/write head assembly (commonly referred to as a head) mounted at the distal end thereof and facing downward. A single arm assembly is associated with the bottom surface of the last disk and has its read/write head assembly mounted at the distal end thereof and facing upward. A double arm assembly is positioned between each pair of disk surfaces and has one of its head assemblies facing upward for association with the bottom surface of the upper disk of the pair of disks and has its other head assembly facing downward for association with the top surface of the lower disk of the pair of disks. All of the heads are vertically aligned so that as the actuator rotates the arm assemblies move the heads in unison over the surface of the disks to position the heads over a selected disk track or surface for normal read/write operation.
A conventional read/write head assembly consists of a ferrite or permalloy core around which is wrapped a coil of wire. The core is a ring-shaped solid with a split or gap in it. The gap is filled with a non-magnetic material, usually glass or aluminum oxide, so that the magnetic leakage field is forced across it when dam is written. The coil is used to induce a magnetic field for writing data or to sense change in magnetic flux direction for reading data. The core is mounted upon a slider, usually a rectangular solid which is shaped to provide aerodynamic lift when the disk rotates. Typically, the end of the slider opposite the core has a beveled edge forming a ramp like surface which provides the initial aerodynamic lift as the disk rotates. One conventional head technology has a slider and core made from the same block of ferrite material and is known as monolithic head technology.
Another newer head technology known as thin film head technology is an adaptation of integrated circuit technology. Instead of a ferrite torrid with a bonded glass gap and wire coil, functionally equivalent elements are layered onto a desirable substrate using a photolithographic technique. Thin film heads are typically built in pairs, with one transducer on each rail of the slider. The end of the slider opposite the transducers is sloped generally by a bevel forming a ramp like edge to provide initial aerodynamic lift as the disk rotates. Both monolithic and thin film head technology are well known today.
The data heads regardless of type are attached to a suspension or gimbal which is connected to the load beam which is connected with a mounting plate to the arm member of the actuator. As is well known the gimbal allows the slider to pitch, roll and move vertically over a limited range but not to change angle with respect to the track or move forward, back or sideways. This gives the slider compliance with the media surface by permitting it to maintain a constant flying height over minor disk irregularities. The physical connection of the head to the gimbal, the gimbal to the load beam and the load beam to the arm member of the actuator are all well known.
In one head assembly arrangement, the head is attached to the gimbal and the rails of the head are substantially parallel to the axis of the arm assembly and the gap for the transducer is positioned at the farthest point from the pivot of the actuator. Such heads are aerodynamically designed to fly over the disk surface during clockwise rotation with the ramp end facing into the direction of rotation of the disk being slightly elevated away from the disk surface with respect to the down stream end. These heads have a landing zone at the disk outer diameter. This arrangement is referred to as having the heads flying forward. Since the gap is at the end of the arm at a point furthest away from the pivot, the required wiring for the transducer is simplified.
In another head assembly arrangement, the head is attached to the gimbal and the mils of the head are substantially parallel to the axis of the arm as described above, but the gap for the transducer is positioned at the point closest to the pivot of the actuator. These heads are also aerodynamically designed to fly over the disk surface during clockwise rotation but have a landing zone at the disk inner diameter. The ramp end of the head facing into the direction of rotation of the disk is slightly elevated away from the disk surface with respect to the down stream end. This arrangement is referred to as having the head flying backward. Since the gap is at the end of the arm at a point closest to the pivot the wiring of the transducer is more difficult. Both types of heads are well known, and have been used in commercially available disk drives. All known disk drives having a rotary actuator have the head assemblies vertically aligned and accordingly use one or the other of the above described head assemblies but do not mix the two types of head assemblies.
When there are two disks upon the spindle the actuator has two single arm assemblies and one double arm assembly. The first single arm assembly has a single downward facing head to fly over the upper surface of the first disk, the double arm assembly has a pair of heads, one head facing upward to fly over the lower surface of the first disk and a second head facing downward to fly over the upper surface of the second disk, and the second single arm assembly with a upward facing head to fly over the lower surface of the second disk. Each of the heads are vertically aligned and move in unison over the surface of the disks when the actuator pivots. Of course, if there are more than two disks the same arrangement applies with a double arm assembly having an upward and downward facing pair of heads positioned between each pair of disk surfaces. The upward and downward facing pair of heads are mounted substantially back to back so that the double arm assembly has two separate gimbals each holding one of the heads and two separate load beams each connected to the arm member with a mounting plate. Accordingly, the space between each pair of disks must be large enough to accommodate the pair of head assemblies each mounted to their respective gimbals and load beams and the arm member that holds them.
The trend in recent years has been to reduce the overall physical size, commonly referred to as form factor, of the disk drive. The spacing between disks mandated by the back to back mounted heads together with their gimbals, load beams and the arm member is recognized by those of ordinary skill in the field as a limiting factor in reducing the size of the disk drives. Efforts to reduce the space needed between disks has lead to the development of thinner sliders and low profile suspensions. Yet any attempt to reduce the space needed between disk surfaces must retain certain physical parameters or characteristics of the arm assembly. For example, the gimbal must be rigidly attached to the load beam but still must have high strength and compliance and both the load beam and arm member must have low mass for fast acceleration with low energy and must be structurally rigid to minimize vibrational resonances in the slider and gimbal. In spite of the recognized desirability of reducing the spacing between disks, all known rotary actuator arms positioned between disks have the head assemblies mounted back to back.
Even with all of these efforts the current arm member is approximately 0.030 inches thick, each head is approximately 0.030 inches thick and each gimbal and load beam is approximately the same. Accordingly, the minimum spacing between disks needed to accommodate the arm assembly with back to back heads remains at approximately 0.090 inches.
In known disk drives, during the manufacturing process, the actuator is independently assembled and mounted onto a baseplate while the disk/spindle assembly is mounted onto the same baseplate. A unitary baseplate is used for rigidity and strength. During the joining of the actuator and disk/spindle assembly, a comb type element is used to separate the arm assemblies of the actuator and lift the heads to the position the heads would have if they were flying over the disk surface. The actuator arm assemblies are then simply rotated to physically merge with the disk/spindle assembly and the comb is removed. The actuator arms are then rotated further to position the heads over their appropriate landing zones or areas.
In another known manufacturing technique referred to as air merge, neither the actuator nor the disk/spindle assembly is attached to the baseplate. The actuator arm assemblies are spaced apart with a comb and the disk/spindle assembly is positioned in a fixture facing the actuator. Now the actuator assembly and the disk/spindle assembly are moved relative to each other and the actuator is merged with the disk/spindle assembly and the comb is removed. The merging continues until the arms position the heads over the respective landing areas. The actuator and disk/spindle assembly are now mounted onto the baseplate. The air merge operation requires complex fixtures to hold the actuator and disk/spindle assembly in the proper position and within tolerances. This process becomes increasingly difficult with smaller form factor drives and is not even possible if the spindle is pre-mounted onto the baseplate as is commonly the case.
In still other known manufacturing processes, the baseplate has been split in numerous ways to facilitate the joining of the parts together. However, in these known split baseplate processes the actuator and disk/spindle assembly have always been mounted on the same portion of the split baseplate to provide stiffness and rigidity.